Re: [RFC v1 0/4] Make KHO Stateless

[Matthew Wilcox <willy@infradead.org>]

On Wed, Sep 17, 2025 at 08:36:09AM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 16, 2025 at 07:50:15PM -0700, Jason Miu wrote:
> > This series transitions KHO from an xarray-based metadata tracking
> > system with serialization to using page table like data structures
> > that can be passed directly to the next kernel.
> > 
> > The key motivations for this change are to:
> > - Eliminate the need for data serialization before kexec.
> > - Remove the former KHO state machine by deprecating the finalize
> >   and abort states.
> > - Pass preservation metadata more directly to the next kernel via the FDT.
> > 
> > The new approach uses a per-order page table structure (kho_order_table,
> > kho_page_table, kho_bitmap_table) to mark preserved pages. The physical
> > address of the root `kho_order_table` is passed in the FDT, allowing the
> > next kernel to reconstruct the preserved memory map.
> 
> It is not a "page table" structure, it is just a radix tree with bits
> as the leaf.

Sounds like the IDA data structure.  Maybe that API needs to be enhanced
for this use case, but surely using the same data structure would be a
good thing?